A marathon is human joy on a grand scale. The training can be solitary, especially on those bleak winter mornings, running in the darkness when all you can hear is your breath and the mad neighborhood dogs. But the race itself is a jubilant parade, loud and visible for spectators and participants: all those runners of different ages and inspirations, motoring fast and slow over familiar streets.

The energy from the crowd will lift you off your feet. Marathoners will complain about the chafed legs and the blisters but they know the truth: this sport is addictive and affirming, whether you finish in two and-a-half hours or six. This is why marathoning has blossomed in this country, especially in the grass roots, where few people are competing against anything other than themselves. The finish is the thing—that's where the real joy is. For many men and women who cross that line, completing a marathon becomes one of the happiest days of their lives.

Explosions Rock Boston

It would be awful anywhere, in any setting. But there is something utterly wicked about it happening at such a public location, near the marathon finish line on the storied concrete of Boylston Street. Just steps from what is traditionally the scene of so much personal triumph—people pushing themselves to limits they never thought they had—there is only madness and horror.

Information from Boston continues to pour in, much of it incomplete, most of it terrifying. The reported tolls are devastating: at least three dead, one of them a child, and about 140 injured. Victims are said to include both spectators and runners; video from the scene is frantic and terrifying. As first responders rushed to attend to victims, there was mayhem and fear and bursts of news that have proven both true and erroneous. Relatives and friends began the nauseating process of trying to connect with loved ones who'd intended to run. Police urged residents to stay home. Officials halted trains and air traffic. On a day of civic celebration, Boston met the evening on a nervous lockdown.

An afternoon unraveled in blunt shock. Patriots' Day in Boston is a brilliantly choreographed sports day—the marathon sets off in the morning, followed by a Red Sox game that begins before lunch and it is possible to finish up at Fenway Park, wander over the Mass Pike and catch a bunch of the race. The marathon has produced some local legends—Bill Rodgers, Joan Benoit Samuelson, Dick and Rick Hoyt—but mostly it's about the crowd. The Boston Marathon may be an elite race in which participants are asked to qualify but what makes it memorable are the little things that make any race special: the visible personal battles, played out on public stage, from Hopkinton to Boston.

This is a city that has won its share of championships and seen its share of championship parades over the past decade, but Patriots' Day is Boston at its best. Though it's a holiday for many, there's a sense of a whole city playing hooky. It's the best Monday in the history of Mondays.

Raw video courtesy of WHDH shows one of the bombs detonating near the finish line of the Boston Marathon.

Now it is not. The athletic aspect of the Boston Marathon feels hopelessly unimportant now, as it should. There are dead, there are injured, there are lives permanently changed and trauma that will never completely fade.

There's also abundant outrage, and justifiably so. The act is unconscionable and the vulnerability is universal. What appears to have happened in Boston could happen anywhere.

In the coming days, it is almost certain that more will be learned about the explosions and the motives behind it. A clearer picture will emerge. There will be eyewitness accounts and mourning and a stillness that comes with heartache. What there won't be—at least for a long time, is a finish line.

The end of Boston Marathon was an exhilarating experience for runners, a sharp right off Commonwealth Avenue onto Hereford Street and then a quick left onto Boylston before all that noise and the thrilling final strides.

That scene, once joyous, is full of pain. Boston is at the beginning of a long, brutal process and the finish now looks, devastatingly, a million miles away.

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